1. Field of the Invention
The present invention relates generally to wireless communications and, more particularly, to a control channel element detection method and apparatus using a Channel Quality Indicator (CQI) in a wireless communication system.
2. Description of the Related Art
Universal Mobile Telecommunications System (UMTS) is one of the 3rd Generation (3G) mobile telecommunication technologies, which has evolved from Global System for Mobile communications (GSM) and General Packet Radio Services (GPRS), and uses Wideband Code Division Multiple Access (WCDMA). The 3rd Generation Partnership Project (3GPP), which is responsible for the standardization of UMTS, is working to significantly extend the performance of UMTS in the work item Long Term Evolution (LTE).
LTE is a 3GPP standard that provides downlink speeds of up to 300 Mbps and is expected to be commercially launched in 2010. In order to fulfill the requirements for the LTE systems, studies are being done on various aspects including minimization of the number of involved nodes in the connections and placing radio protocol as close as to the radio channels.
In an LTE system, a Physical Downlink Control CHannel (PDCCH) carries resource allocation information for a downlink shared channel and an uplink shared channel. A base station (e.g., an evolved Node-B (eNB) transmits the PDCCH to individual mobile stations (e.g., User Equipments (UE)). PDCCHs are transmitted on one or several Control Channel Elements (CCEs), where a CCE corresponds to 9 Resource Element Groups (REGs).
The PDCCH is located in the first three Orthogonal Frequency Division Multiplexing (OFDM) symbols of each subframe. The resource scheduling information of the PDCCH is mapped from the 0th subcarrier of the 0th OFDM symbol. The resource scheduling information of the PDCCH includes the resource allocation information such as a number of OFDM symbols, transmission format, and retransmission information. Also, the downlink reference signals are transmitted in the same resource space as the PDSCH. Other downlink control channels are mapped to the remaining resource space, i.e., where the PDCCH resource allocation information and the reference signals are not mapped.
When a base station is serving multiple mobile stations, each mobile station can locate the resources allocated for transmission and/or reception of data, based on the control information included in the PDCCH. The base station maps the control channel elements carrying the PDCCHs for the mobile stations into the resource space in a sequential order. Accordingly, each mobile station searches the entire PDCCH resource space for the PDCCH destined for itself with all the potential CCE formats. Although the CCE search process is simple, the repeated CCE searching steps may cause a processing delay. Consequently, such a processing delay can be burdensome for the power-constrained mobile stations.